CP-M Z80 home brew computer circuit board

[Chuck Guzis]

> Date: Sun, 15 Jun 2008 17:22:48 -0400
> From: "Roy J. Tellason" 

> I thought it was the 179x parts that had the data separator on-chip, 
> no?

Nope.  The 179x require an external data separator, as well as 
precomp ciruitry and floppy-interface buffering, as well as requiring 
+12 (although the Fujitsu clones need only +5).  It's the 279x that 
have the internal data separators, but the 1770/72/73 have just about 
everything in a neat little 28-pin package.  About all you have to 
supply is side and unit-select logic, which is easily done with a 
write-only latch.  Add address decoding logic and you're pretty much 
done.  DMA not required.  This contributed hugely, IMOHO, to their 
being popular on a number of low-end "home" computer systems.  The 
chip handles motor control (e.g. spin-up time from from motor on to 
ready, auto motor-off after a certain number of inactive revs), which 
the 179x doesn't do.

The 765-based all-in-ones such as the National 8473 and the WD37C65A 
are about as hard to obtain and are a little more difficult to 
interface to a Z80 (just about require DMA and interrupts to work 
right).

Cheers,
Chuck